A projector can be exemplified as a display device that is increasingly used recently. Advantageously, the projector can easily realize a large-sized screen. The projector operates in the following way, in which light emitted from a light source is synthesized by a light synthesizer to become image light, and this image light is projected onto a screen through a lighting system such as a lens.
Representative examples of a screen displaying an image by the projector include a transmissive screen where an image is projected from the rear of the screen, and a reflective screen reflecting projection light projected from a projector in front of the screen to allow a projection image to be viewed by reflected light.
Representative examples of a related art reflective screen include a bead screen and a white screen reflecting and scattering projected light from a projector. However, since these screens reflects not only projection light from the projector but also external light, the contrast of an image reduces at an atmosphere where an external light level is high, so that a user cannot accurately view a desired image. Therefore, the user should draw a curtain to reduce an external light level to view a projector in an indoor space where the external light level is high. For this limitation, the projector has not been widely distributed for a general household and has required a separate installation space.
To solve this limitation, technology of improving a contrast even when an external light level is higher than a predetermined level by installing a light absorption layer in front of a reflective layer has been proposed. Korean Patent Registration No. 10-0259436 (related art 1) discloses technology in which a light reflection layer is formed on the front side of a substrate, and a light diffusion layer where a pigment allowing light absorption to occur is combined is formed on the front side of the light refection layer.
However, in this case, since not only external light but also projection light from the projector reduces by the light diffusion layer, a white color level falls down, brightness (screen gain) reduces, and contrast enhancement is limited. Particularly, since light incident to the reflection layer and light reflected by the reflection layer are greatly absorbed by the pigment while passing through the light diffusion layer, the above-described limitation becomes serious.
To solve the limitation of the related art 1, Korean Patent Publication No. 10-2006-0045116 (related art 2) discloses a screen having a structure in which a plurality of selective reflection layers and diffusion layers are sequentially stacked on a substrate. Here, the principal technical contents of the selective reflection layer are to allow wavelength regions of three colors of red (R), green (G), blue (B) to be appropriately reflected, thereby improving the quality of a reflection image.
However, according to the technical contents of the related art 2, though an image of high brightness and high contrast of some extent can be obtained under an atmosphere of a high external light level, a plurality of manufacturing processes are required to stack a metal layer, a dielectric layer, and a light absorption thin layer having transmittance on a substrate. Particularly, a sputtering equipment is required to deposit the metal layer and thus manufacturing cost increases. Also, a screen price increases to exceed the cost of a projector, so that there are lots of limitations in commercialization.